This invention relates to photographic materials for a diffusion transfer process wherein images of metallic silver or dyes are formed by diffusion transfer. More particularly, the invention is concerned with novel photographic materials suitable for use in such the diffusion transfer process (which materials are hereinafter referred to as diffusion transfer photographic materials) in which materials alkalinity, increased in the system when development is carried out, can be substantially decreased without interferring with the formation of diffusion transfer images.
As diffusion transfer photographic materials have been hitherto known silver salt diffusion transfer photographic materials and color diffusion transfer photographic materials.
In silver salt diffusion transfer photographic materials, a light-sensitive silver halide emulsion, after imagewise exposed to light, is developed with an alkaline processing composition. The image-forming substance comprising a silver complex salt formed from the silver halide in the unexposed area by use of a silver halide solvent or a complex forming agent is diffused to a silver-precipitating layer (or an image-receiving element) to give a positive image.
In color diffusion transfer photographic materials, a light-sensitive silver halide emulsion, after imagewise exposed to light, is developed with an alkaline processing composition. Simultaneously, an imagewise distributed image is formed by a color image-forming substance. At least a part of the color image-forming substance is transferred to an image-receiving layer superposed on the emulsion to give a positive image.
Thus, in both silver salt and color diffusion transfer photographic materials, development with an alkaline processing composition is employed for the purpose of the image formation.
In these diffusion transfer photographic materials, however, the presence, after the formation of transfer images, of the alkaline processing composition in the system can cause the diffusion of undesired image-forming substances and contaminate the image-receiving layer. Among attempts to overcome this drawback to obtain excellent images, the use of a layer has been proposed which layer contain a neutralizing agent to stop the development at a desired stage and to lower a pH value less than the one at which the image-forming substance is rendered nondiffusible. Such the layer is hereinafter referred to as "netralization layer.".
The neutralization layer may be provided anywhere in diffusion transfer photographic materials, although it is, in ageneral provided between an image-receiving layer and the support therefor, between a light-sensitive layer and the support therefor, or in a processing sheet. As representatives of the neutralizing agent which can be incorporated into the neutralization layer, there have been disclosed, for example, polymeric acids or low molecular acids in U.S. Pat. Nos. 2,584,030 and 3,362,819. These polymeric acids or low molecular acids, however, have such drawbacks that they cause a distortion of the resulting image, that their capacity for neutralization, after a long storage, is reduced by the influence of moisture and temperature, and that photographic materials containing them is deformed in shape by such influences. Further, the so-called yellow stainning is often observed in the images formed.
Furthermore, the conventional neutralizing agents show poor water-solubility, so that, in coating neutralization layers therewith, the undesirable use of organic solvents toxious to human is required.
An object of the present invention is to provide a diffusion transfer photographic material having incorporated thereinto a neutralization layer containing a novel neutralizing agent.
Another object of the invention is to provide a diffusion transfer photographic materials containing a novel neutralizing agent whereby images can be obtained which exhibit excellent storability, high color density and color purity, marked light stability, less stainning and no distortion.
Still another object of the invention is to provide a diffusion transfer photographic material containing a novel neutralizing agent which exhibits proper water-solubility.